The present invention relates to support roll assemblies and a novel method of assembling support rolls.
U.S. Pat. No. 1,362,910 discloses a support roll rotatably mounted in axial openings of a frame structure wherein the outer ring of a ball bearing assembly is inserted over an inner part which engages a helical spring on its seating face in the bore of the support roll. In order to provide an appropriate axial clearance of the outer ring in the support roll, it is necessary to provide a narrow radial sliding play between the outer peripheral surface of the outer ring and its seating face in the bore of the support roll. Consequently, manufacture of the support roll is quite expensive by reason of the required critically narrow fabrication tolerances. The necessary sliding play between the outer ring and the support roll is also undesirable in applications requiring accurate bearing support of the support pins with little radial out of balance of the support roll in operation. Additionally, it has been found that installation and assembly of a support roll of this type has certain disadvantages and drawbacks since the outer ring guided with sliding play on its seating face in the support roll may become cocked during axial insertion in the support roll and therefore become jammed. Consequently, the outer ring can be inserted in the support roll over the inner parts and the balls of the ball bearing only by overcoming high bending forces. The danger then exists that the outer and inner race of the bearing are likely to be damaged at the ball contact locations. The assembly process of the support roll of U.S. Pat. No. 1,362,910 is also somewhat cumbersome since a helical spring must be fitted between the outer ring of the ball bearing and a radial shoulder face of the support roll during installation of the bearing in the support roll.
With the foregoing in mind, it is an object of the present invention to provide an improved support roll assembly which eliminates some of the drawbacks and disadvantages of the prior assemblies discussed above. To this end, the support roll assembly includes a bushing mounted in the bore of the support roll at opposite axial ends, a bearing assembly housed in the bushing comprising an outer ring of strip steel having a cylindrical outer race for the balls and a thrust shoulder facing radially inwardly. The assembly further includes an elongated cylindrical member the inner part of which has a raceway for a row of balls and the outer part defines a support pin engageable in openings in the axially spaced support frame members. The cylindrical member has an axial bore for securing the inner part in the opening in the frame by means of a fastening screw member. A sealing plug made of an elastically compressible plastic material engages in the central bore formed at the inner end of the thrust shoulder. By this arrangement, during assembly of the support roll between the frame members, the inner part of the cylindrical member is moved axially inwardly against the elastically yielding wall of the sealing plug and when the support pin aligns with the openings in the opposing frame members, the fastening screw is simply turned to draw the inner part axially outwardly and the assembly of the roll between the frame members is completed. By this arrangement, the danger of overstressing the balls of the bearing assembly during axial insertion of the inner part against the elastic means in the support roll is thus prevented. It is also noted that the assembly process is greatly simplified and at the same time provides a relatively accurate radial bearing support of the support pins of the support roll in the openings of the associated frame members.
In the roll assembly of the present invention, the outer ring is mounted in the bore of the support roll by a tight or press fit which may be accomplished over a relatively wide range of fabrication tolerances which makes manufacture rather economical. Furthermore, by this arrangement, the outer ring is locked in place without radial play in the support roll producing in operation a good smooth running of the support roll. The elastic sealing plug is simple and easy to assemble for installation of the bearing in the support roll at the radially inner end of the outer ring and since the elastically yielding wall of the sealing plug during axial insertion of the inner part abuts or engages the inner axial end of the inner part, this wall as an elastic means which at least partly relieves the balls of the bearing during insertion of the inner part against the thrust shoulder of the outer ring. Thus, a harmful overstressing of the balls during installation of the support pins of the support roll is prevented in this way.
When the fastening screw is threaded into the cylindrical member, the inner axial end displaces the sealing plug to break contact with the support pin thereby eliminating sliding friction between the inner axial end face of the cylindrical member and the sealing plug.
One of the features of the roll assembly of the present invention is the particular configuration of the sealing plug which engages in the bore of the thrust shoulder of the outer ring of the bearing and which during assembly of the support roll between the frame members is in pressure applying relation with the support pin to automatically urge it into the openings in the frame members when it is aligned therewith and which upon assembly of the fastening screw is displaced out of pressure-applying relation to minimize friction during operation of the roll assembly and provides a seal for the annular spaced within which the rolling elements are disposed. To this end, the sealing plug includes an enlarged head portion, a shank having two axially spaced grooves formed therein within which the wall of the thrust shoulder defining the bore seats and a flexible resilient sealing lip at the inner axial end of the shank. Accordingly, when the parts are assembled the sealing plug is pressed in so that the thrust shoulder engages in the innermost groove adjacent the head and now as the elongated cylindrical members at each end are displaced inwardly to allow positioning between the frame members, the elongated cylindrical members at their inner end are in pressure-applying relation with the shank of the plug portion. Now when the support pin is aligned with the opening in the frame member, the elasticity of the plug displaces the elongated cylindrical members outwardly so that the support pin is seated in the opening in the frame member. The fastening screw is then turned into the elongated cylindrical member so that its inner tip end thereof projects beyond the inner end of the cylindrical member to engage the shank portion of the sealing plug and displace it axially so that the thrust shoulder engages in the second annular groove adjacent the sealing lip. More specifically, while the fastening screw is threaded in, the free end of the thrust shoulder snapped in the annular groove of the sealing plug is namely taken from the annular groove to the subsequent conical outside surface of the sealing plug as a result of elastic compressibility of the sealing plug construction material. The sealing plug then presses with its conical outside surface radially outward against the free end of the thrust shoulder so that the sealing plug begins to slide in reaction to the bore surface of the free end of the thrust shoulder. The sealing plug, accordingly, axially moves into the support roll until a radially outward acting elastic power is no longer applied at the radial inner end of the conical surface by the sealing plug or until a radially outward projecting shoulder surface of the sealing plug comes to rest against the outside front face of the free end of the thrust shoulder and consequently impedes a further sliding of the sealing plug in the bore of the free end and at the same time seals the bearing space of the ball bearing towards the inside of the support roll.
In accordance with another feature of the present invention, the sealing plug may be formed as a hollow bulbous member filled with a pressurized fluid and mounted in the opening in the thrust collar with its elastically arched thin wall section aligned with the axial opening in the support pin. Consequently, when the fastening screw is threaded into the support pin, its pointed inner tip end penetrates the elastically arched thin-walled section of the sealing plug whereby the fluid under pressure in the hollow space is discharged into the chamber of the bearing assembly thus relieving the pressure contact with the inner end of the support pin and thus minimizing frictional contact and ensuring smooth running operation of the support roll. The hollow chamber may be filled with a lubricant under pressure so that upon penetration of the elastically arched thin-walled section, the lubricant is discharged into the bearing space and uniformly distributed in the bearing to lubricate the same.
In accordance with another feature of the present invention, the support pin is stepped at its outer axial end to define a shoulder limiting axial outward displacement of the support relative to the frame member when the support pin has been seated in the opening therein.
If the support roll has been stored for some time in a dusty environment, dust or dirt may accumulate in the outer area of the sealing gap of the bearing. In this instance, during penetration of the hollow space of the sealing plug filled with compressed gas, the dust or dirt is blown outward from the sealing gaps of the bearing space to eliminate problems in operation resulting from particulate matter in the bearing.